Video player/recorder machines have become very popular for entertainment and other uses. Both the number of hours these machines are used and the number of times they are used have greatly increased. With such an increase in use of video machines, a corresponding increase has occurred in the need to clean the machines. In operation, magnetic oxides may shed off of a tape and may adhere to a head of the machine and its transport system, resulting in inconveniences such as turbulence, dropout, irregular color and color fadeout, upward shifting of a tape, pollution of the pinch roller, and other contamination problems. Dust or other foreign matter may also find its way into the tape path. The problem of foreign matter and oxide accumulation is intensified when rental tapes are used in a machine. Rental tapes are typically lower quality tapes and may be dirtier or have more oxides due to their being used over and over again in uncontrolled environments.
Typically the VHS video player/recorder machine includes a video head drum that contains one or more video heads and also possibly audio heads. The head drum either records or plays back the video portion of a playing tape. The machine also contains a stationary audio head that performs the same function for the sound portion of the tape, an erase head, and other components that engage the tape. To avoid the problems discussed above, the surface portions of at least the video and audio heads, and in some instances other components that contact the playing tape, should be cleaned periodically.
Particularly for video cassette player/recorders, this cleaning operation can be rather difficult. In a typical cassette player/recorder, there is a rectangular cassette recess into which the cassette containing the playing tape is placed. The video head drum and the audio head of the machine are positioned within the housing of the player/recorder and are spaced a moderate distance away from the open cassette recess. When the player/recorder is operated, a number of guides that are part of the player/recorder apparatus engage the tape in the cassette case and move the tape outwardly into engagement with the playing/recording heads. The locations of these heads are sufficiently inaccessible so that cleaning the heads by means of some manually operated instrument is at best a clumsy operation and can possibly damage the more delicate components.
Another problem is that the video playing/recording head drum is a delicate component that should be handled with a high degree of care. A typical video head drum is in the shape of a disc having a circumferential operating surface that engages the surface of the playing tape. On the peripheral surface of the video head, there is at least one (and in some instances a plurality) of video heads. The head drum generally has a multitude of grooves extending circumferentially around the perimeter of the operating surface. When these grooves are clean, they help provide an air bearing between the videotape and the head drum to minimize friction. The video head drum is mounted for rotation about a circular path that is slightly angled or canted with respect to the longitudinal axis of the playing tape. In operation, the video head drum rotates at a very high rate, in the order of one to two thousand revolutions per minute, with the heads scanning the tape on each revolution. In bringing any sort of cleaning device into contact with the video head drum, extreme caution should be exercised in avoiding any damage to the operating elements of the video head. Also, with the video head drum rotating at such high speed, the torque of the drive for the video head drum is necessarily small, so that care should be exercised in not creating any substantial amount of frictional resistance against the peripheral surface of the head, since it is possible that such resistance would substantially reduce the rate of rotation and possibly damage some of the operating components. Many machines have an automatic shutoff that is activated when excess frictional resistance is applied to the drum.
Cassette cleaners have been developed that have a cassette housing in which a cleaning ribbon is mounted. In operation, the cassette housing is placed into the playing receptacle of the player/recorder, and the start knob or button is moved to the "on" or "play" position so that guide members of the player/recorder engage the cleaning ribbon and bring it into engagement with at least the drum of the video head and, in some instances, the other operating components that would normally come into contact with the playing tape. The cleaning action is further assisted by applying a cleaning solution to the ribbon.
The cleaning ribbon typically is mounted on spools within the cassette housing so that, after it is moved out of the cassette housing into cleaning engagement with the drum (and possibly other components of the player/recorder), the cleaning ribbon moves along its axial length at substantially the same rate of speed as the magnetic tape in the normal mode of operation of the player/recorder. Due to the high speed of the video head, there is relative movement between the cleaning ribbon and the drum of the playing head.
One of the major problems in providing such cassette cleaners is the sensitivity of the operating components of the various player/recorders, as discussed above. For example, like the cleaning cassettes, the cassettes for magnetic tapes generally have two spools that engage spindles of the player/recorder. During normal operations, the magnetic tape will be unwound from one spool and wound onto the other. If the head drum or possibly the spindles sense a resistance to rotation greater than a certain level, this will generally activate a shutoff mechanism in the player/recorder. The reason for this is that the increased resistance indicates a problem, and the player/recorder shuts off to avoid damage to the magnetic tape. A number of player/recorders also have other shutoff mechanisms. This can be particularly problematic since the air-bearing surface created between a normal playing tape and the drum by the grooves is not provided between the cleaning ribbon and the drum since the cleaning ribbon is air permeable due to its fabric-like construction.
Another problem of such cassette cleaners arises due to the fact that the cleaning tape is of similar width to a magnetic videotape. The cleaning tape cleans only the area of the components that normally come into contact with a magnetic videotape. Thus, any dirt deposits outside these areas are not removed. This may be a significant problem since most dirt deposits build up on the components on either side of the tape path. These deposits eventually enter the path of the tape, thus reducing the picture and sound quality and causing dirt to be transferred to other components. Ribbon cleaners also have limited capabilities when used with head drums that have grooves formed in their outer periphery. The ribbon does not clean within the grooves and they become collection areas for dirt.
An attempt to deal with the problems of dirt buildup at the edges of the normal tape path and cleaning of drum grooves is disclosed in U.S. Pat. No. 4,761,700 (Fritsch). The Fritsch patent includes a cleaning ribbon and a brush that is activated by movement of the ribbon. The cleaning ribbon encounters frictional contact with the pinch roller and capstan, the audio recording head, a number of guide members, one side of the drum, a brush activation mechanism, the other side of the drum, and the erase head. The brush contacts the drum between the two cleaning ribbon drum contact areas.
Because the brush of the Fritsch device is operatively connected to the cleaning ribbon, the brush cannot operate without the ribbon. Also, the extensive path of the ribbon, including its use to activate the brush and hold it in place while cleaning, introduces extensive frictional resistance on the spindles of the player/recorder. This resistance may cause the player/recorder to shut off, the cleaning benefits thus not being realized. The double contact of the ribbon on the drum combined with the brush contact may also cause excessive resistance on the drum, particularly if a cleaning solution is used on the brush and/or cleaning ribbon.
Because of the above-discussed limitations of the known cassette-cleaning devices, there is a need for a cleaning device that effectively cleans the components of player/recorder machines, that is compatible with most machines, and that does not introduce excessive frictional resistance on either the drum or the spindles of the machine.